Re: [Patch bpf-next v4 03/11] skmsg: introduce skb_send_sock() for sock_map

From: Cong Wang <redacted>

We only have skb_send_sock_locked() which requires callers
to use lock_sock(). Introduce a variant skb_send_sock()
which locks on its own, callers do not need to lock it
any more. This will save us from adding a ->sendmsg_locked
for each protocol.

To reuse the code, pass function pointers to __skb_send_sock()
and build skb_send_sock() and skb_send_sock_locked() on top.

Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jakub Sitnicki <jakub@cloudflare.com>
Cc: Lorenz Bauer <redacted>
Signed-off-by: Cong Wang <redacted>
---
 include/linux/skbuff.h |  1 +
 net/core/skbuff.c      | 52 ++++++++++++++++++++++++++++++++++++------
 2 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 0503c917d773..2fc8c3657c53 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h

@@ -3626,6 +3626,7 @@ int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
 		    unsigned int flags);
 int skb_send_sock_locked(struct sock *sk, struct sk_buff *skb, int offset,
 			 int len);
+int skb_send_sock(struct sock *sk, struct sk_buff *skb, int offset, int len);
 void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
 unsigned int skb_zerocopy_headlen(const struct sk_buff *from);
 int skb_zerocopy(struct sk_buff *to, struct sk_buff *from,

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 545a472273a5..396586bd6ae3 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c

@@ -2500,9 +2500,12 @@ int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
 }
 EXPORT_SYMBOL_GPL(skb_splice_bits);

-/* Send skb data on a socket. Socket must be locked. */
-int skb_send_sock_locked(struct sock *sk, struct sk_buff *skb, int offset,
-			 int len)
+typedef int (*sendmsg_func)(struct sock *sk, struct msghdr *msg,
+			    struct kvec *vec, size_t num, size_t size);
+typedef int (*sendpage_func)(struct sock *sk, struct page *page, int offset,
+			   size_t size, int flags);
+static int __skb_send_sock(struct sock *sk, struct sk_buff *skb, int offset,
+			   int len, sendmsg_func sendmsg, sendpage_func sendpage)
 {
 	unsigned int orig_len = len;
 	struct sk_buff *head = skb;

@@ -2522,7 +2525,7 @@ int skb_send_sock_locked(struct sock *sk, struct sk_buff *skb, int offset,
 		memset(&msg, 0, sizeof(msg));
 		msg.msg_flags = MSG_DONTWAIT;

-		ret = kernel_sendmsg_locked(sk, &msg, &kv, 1, slen);
+		ret = sendmsg(sk, &msg, &kv, 1, slen);

 		if (ret <= 0)
 			goto error;

@@ -2553,9 +2556,9 @@ int skb_send_sock_locked(struct sock *sk, struct sk_buff *skb, int offset,
 		slen = min_t(size_t, len, skb_frag_size(frag) - offset);

 		while (slen) {
-			ret = kernel_sendpage_locked(sk, skb_frag_page(frag),
-						     skb_frag_off(frag) + offset,
-						     slen, MSG_DONTWAIT);
+			ret = sendpage(sk, skb_frag_page(frag),
+				       skb_frag_off(frag) + offset,
+				       slen, MSG_DONTWAIT);
 			if (ret <= 0)
 				goto error;